Mobile devices, including smart phones, by their very nature require the ability to operate without being wired to an external power supply. To satisfy this requirement, mobile devices typically are powered by rechargeable batteries. Unfortunately, the rechargeable batteries installed in mobile devices are conventionally configured such that those mobile devices must periodically engage with a wired power supply in order to recharge their batteries, and thereby becoming “non-mobile” while recharging or require manual battery replacement.
In addition, many standard devices, such as smoke or gas detectors, within houses and commercial buildings require continuous maintenance because of their dependence on battery power. This can be quite laborious and in some cases detrimental to health and safety when batteries are not changed on time. Some new buildings have these wired into the internal electoral circuits, but this can be quite expensive to retrofit to an old building. A way to keep these devices automatically powered or charged would keep people much safer, saving lives in the case of emergencies.
Because of the increased use of mobile devices such as mobile phones, televisions and Wi-Fi networks, radio frequency (RF) waves are common all over the world, especially inside of buildings. While technology to convert RF waves into usable power exists, it is not efficient or strong enough to use the power harnessed in any commercial setting.
Currently available wireless recharging solutions depend on close proximity and/or precise placement of the device to be recharged and utilize mains power or another power source as a source of energy. Because of the availability of RF waves in modern society, a new RF harnessing technology has the potential to transform the way small and mobile devices are powered.
A Power-Efficient Radio Frequency Energy-Harvesting Circuit by Philip Khoury discloses a thesis exploring radio frequency (RF) energy harvesting, specifically on the design of a rectenna circuit. The thesis investigates an ideal antenna design, focusing on a Koch fractal loop antenna to increase overall efficiency in low level power conversions. Former works are consulted as the author finds an ideal design consisting of a seven-element Greinacher rectifier and several multi-pronged, multi-frequency Koch loop and meandered open stub antennas. This final design was simulated with a software package over a variety of radio frequencies.
RF Energy Harvesting for the Low Energy Internet of Things a publication by Drayson Technologies describing a high efficiency, radio frequency energy-harvesting system. It discusses a standard harvester for collecting and converting ambient radio frequency to power low energy devices. This harvester generally consists of an antenna, an impedance matching network, a non-linear component and an RF filter and power management module. The antenna may vary for application of different ranges of wavelengths but the antenna is configured for one specific range of wavelengths.
Ambient Electromagnetic Wireless Energy Harvesting using Multiband Planar Antenna a publication by Nimo et al. discusses an approach to electromagnetic energy gathering using planar antennas. A simple circuit is discussed to convert the signal from the antenna to DC power. The general aim of the thesis is to optimize an antenna implemented to maximize efficiency of energy collection from an ambient electromagnetic concentration. This publication discloses that using a multiband/broadband harvesting will improve the efficiency of an electromagnetic harvester of RF waves.
Design Optimization and Implementation for RF Energy Harvesting Circuits by Ufuk Muncuk discusses a variety of configurations to maximize RF energy harvesting. Specifically, it optimizes the number of rectifier stages for the efficiency of energy harvesting as well a simulation of several sub-circuit stage arrangements as well as simulates the difference of different types and amount of antennas used. Overall, Muncuk optimizes an RF energy harvesting circuit by changing the number rectifier stages as well as different types and amounts of antennas, optimizing current technologies through computer simulation.